The demand for lower purity oxygen is increasing in applications such as glassmaking, steelmaking and energy production. Lower purity oxygen is generally produced in large quantities by the cryogenic rectification of feed air in a double column wherein feed air at the pressure of the higher pressure column is used to reboil the liquid bottoms of the lower pressure column and is then passed into the higher pressure column.
In some situations it may be desirable to produce some high purity nitrogen in addition to gaseous oxygen product. Such dual product production cannot be efficiently accomplished with a conventional lower purity oxygen plant.
Accordingly, it is an object of this invention to provide a cryogenic rectification system which can effectively and efficiently produce both gaseous oxygen and high purity nitrogen.